The population growth, the expansion of the city and the increase of the automotive park of the canton Cuenca has caused a deterioration in air quality, which puts at risk the agricultural production in the nearby rural areas, the objective of the present study was to determine the concentration of Pb in the foliage of cabbage lettuces in the San Joaquín parish. Twelve lettuces of cabbage were planted in two beds that were located in open-pit and greenhouse conditions with a common substrate soil for the development of the plants, the substrate was characterized, the results showed that the content of lead in the foliage of the Lettuce came mostly from the air. At the time of harvest, foliage samples were sent for the analysis of the Pb content by the atomic absorption method, the lowest value corresponded to the greenhouse crop with an average of 0,066 mg / kg, while the open crop obtained value of 0,087 mg / kg, according to the independent T-test, there is no significant statistical difference, these values of lead concentration are below the limits established by the World Health Organization, which is considered that lettuces they are not contaminated with Pb associated with vehicles and fuels. [ABSTRACT FROM AUTHOR]